---
id: wiki-2026-0508-debugger-techniques
title: Debugger Techniques
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Debugging, Debug Tooling]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [debugging, devtools, troubleshooting]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: applied
tech_stack:
  language: Multi
  framework: gdb/lldb/Chrome DevTools
---

# Debugger Techniques

## 매 한 줄
> **"매 print 보다 breakpoint 가 빠르고, breakpoint 보다 reverse-debug 이 깊다."**. Debugger techniques 는 breakpoint, watchpoint, conditional, log-point, time-travel, post-mortem (core dump) 의 매 toolkit. 2026 stack: Chrome DevTools (live), VS Code DAP, gdb/lldb, rr (record-replay), Pernosco (cloud time-travel).

## 매 핵심

### 매 Breakpoint Type
- **Line**: 매 source line 정지.
- **Conditional**: 매 expression true 일 때만.
- **Log-point** ("tracepoint"): 매 정지 안하고 log 찍음.
- **Function**: 매 fn enter.
- **Watchpoint**: 매 memory address change.
- **Exception**: 매 throw caught/uncaught.
- **DOM**: 매 Chrome — node modification.
- **XHR/fetch**: 매 URL pattern.
- **Event listener**: 매 click/keydown 등.

### 매 Time-Travel Debugging
- **rr** (Linux): record once, replay backwards/forwards — 매 nondeterministic bug 의 답.
- **Pernosco**: rr trace 의 cloud UI — 매 expression 의 모든 변경 이력.
- **WinDbg TTD** (Windows).
- **Chrome DevTools "Replay panel"** (2025+ experimental).

### 매 응용
1. Heisenbug — 매 conditional + log-point.
2. Crash post-mortem — 매 core dump + gdb.
3. Performance — 매 sampling + breakpoint.
4. Memory leak — 매 heap snapshot diff.
5. Distributed — 매 OpenTelemetry trace.

## 💻 패턴

### Chrome conditional breakpoint
```javascript
// 매 in DevTools right-click line → Add conditional breakpoint
// expression: user.id === 42 && cart.total > 1000
// 또는 logpoint: console.log('cart', cart, 'time', performance.now())
```

### gdb scripted debugging
```bash
gdb --batch -x debug.gdb ./app core.12345
# debug.gdb
set pagination off
bt full
info threads
thread apply all bt
print *some_struct
```

### lldb Python script
```bash
(lldb) script
>>> frame = lldb.frame
>>> for var in frame.variables: print(var.name, var.value)
```

### rr record-replay (Linux)
```bash
rr record ./buggy_program
rr replay
# 매 in rr's gdb
(rr) reverse-continue
(rr) reverse-step
(rr) watch -l some_var
```

### Node.js inspector + Chrome
```bash
node --inspect-brk=0.0.0.0:9229 server.js
# 매 chrome://inspect
```

### Python pdb / debugpy
```python
import pdb; pdb.set_trace()        # 매 classic
breakpoint()                       # 매 PEP 553 (python 3.7+)
# 매 VS Code remote: debugpy.listen(('0.0.0.0', 5678)); debugpy.wait_for_client()
```

### eBPF dynamic tracing
```bash
sudo bpftrace -e 'uprobe:./app:malloc { @[ustack] = count(); }'
```

### Conditional log-point pattern
```javascript
// 매 production-safe lazy log — no perf cost when disabled
if (DEBUG) console.log('state', JSON.stringify(state));
// 매 better — feature flag gated
if (flags.debugCart) logger.debug({ cart, user });
```

## 매 결정 기준
| 상황 | Tool |
|---|---|
| Web (Chromium) | DevTools Sources panel |
| Node.js | --inspect + DevTools / VS Code |
| C/C++ Linux | gdb / lldb + rr |
| C/C++ macOS | lldb + Instruments |
| Python | debugpy + VS Code |
| Heisenbug | rr + Pernosco |
| Production crash | core dump + gdb |
| Distributed | OTel trace |

**기본값**: 매 IDE breakpoint → 부족시 rr / TTD.

## 🔗 Graph
- 부모: [[중단점 (Breakpoints)]]
- 변형: [[동적 런타임 분석 (Dynamic Runtime Analysis)]]
- 응용: [[Flame_Graphs]] · [[Logging_and_Error_Handling]]
- Adjacent: [[Analyze runtime performance]]

## 🤖 LLM 활용
**언제**: stack trace 해석, log clustering, hypothesis generation, repro script.
**언제 X**: 매 step-into 같은 deterministic 작업 — IDE 가 직접.

## ❌ 안티패턴
- **printf-only**: 매 build cycle 낭비 — debugger 사용.
- **Production breakpoint**: 매 thread freeze — log-point 사용.
- **No source map**: 매 minified frame 해독 불가.
- **Trust gut without repro**: 매 unreliable repro 면 가설 무한 반복.

## 🧪 검증 / 중복
- Verified: Chrome DevTools docs; gdb manual; rr-project.org; Pernosco docs.
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — breakpoint taxonomy + rr/TTD + multi-lang |